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Wood properties of trembling aspen and paper birch after 5 years of exposure to elevated concentrations of CO2 and O3

Kostiainen, Katri, Kaakinen, Seija, Warsta, Elina, Kubiske, Mark E., Nelson, Neil D., Sober, Jaak, Karnosky, David, F., Saranpaa, Pekka, Vapaavuori, Elina
Tree physiology 2008 v.28 no.5 pp. 805
forest trees, plant response, Populus tremuloides, Betula papyrifera, elevated atmospheric gases, carbon dioxide, ozone, greenhouse gases, wood chemistry, tree growth, uronic acids, plant extracts, lignin, cell walls, carbohydrates, stemwood, climate change, wood anatomy
We investigated the interactive effects of elevated concentrations of carbon dioxide ([CO2]) and ozone ([O3]) on radial growth, wood chemistry and structure of five 5-year-old trembling aspen (Populus tremuloides Michx.) clones and the wood chemistry of paper birch (Betula papyrifera Marsh.). Material for the study was collected from the Aspen FACE (free-air CO2 enrichment) experiment in Rhinelander, WI, where the saplings had been exposed to four treatments: control, elevated [CO2] (560 ppm), elevated [O3] (1.5 x ambient) and their combination for five growing seasons. Wood properties of both species were altered in response to exposure to the treatments. In aspen, elevated [CO2] decreased uronic acids (constituents of, e.g., hemicellulose) and tended to increase stem diameter. In response to elevated [O3] exposure, acid-soluble lignin concentration decreased and vessel lumen diameter tended to decrease. Elevated [O3] increased the concentration of acetone-soluble extractives in paper birch, but tended to decrease the concentration of these compounds in aspen. In paper birch, elevated [CO2] decreased and elevated [O3] increased starch concentration. The responses of wood properties to 5 years of fumigation differed from those previously reported after 3 years of fumigation.